Speed control system for electrically powered tools of the trigger controlled type



June 27, 1967 GAwRoN 3,132,513

A. F1 SPEED CONTROL SYSTEM FOR ELECTRICALLY POWERED TOOLS OF THE TRIGGER CON'I'ROLLEDy TYPE Original Filed Aug. 19, 1965 United States Patent O 3,328,613 SPEED CONTROL SYSTEM FOR ELECTRICAL- LY POWERED TOOLS OF THE TRIGGER CON- TROLLED TYPE Alex F. Gawron, Chicago, Ill., assignor to Skil Corporation, Chicago, Ill., a corporation of Delaware Continuation of application Ser. No. 481,054, Aug.

19, 1965. This application Oct. 26, 1966, Ser. No. 589,761

4 Claims. (Cl. S10- 48) This invention relates to a speed control system for electrically powered tools of the trigger controlled type, and more particularly-to new and improved means for associating or connecting a trigger with a variable resistor or potentiometer forming part of such a speed control system. This application is a continuation of my application, Ser. No. 481,054, filed Aug. 19, 1965, now abandoned, which application is a continuation-in-part of my `application Ser. No. 438,627, filed Mar. 10, 1965, now

Patent 3,209,228.

A primary object of the invention is to provide a rotary potentiometer in association with a speed control circuit system, which potentiometer serves as the variable resistor in the circuit, and to provide a trigger associated with the rotary element of the potentiometer in a novel manner so that actuation of the trigger causes rotation of the rotary element of the potentiometer.

Another object of the invention is to provide a new and improved speed control unit for a hand manipulatable electric tool, which unit includes a casing mounting a rotary potentiometer'and a trigger, wherein the trigger is uniquely associated with the rotary element of the potentiometer for operation of the latter upon actuation of the trigger. v These and other objects and advantagesof the invention will become apparent from the following specification disclosing a preferred embodiment of the invention wherein: FIG. 1 is a fragmentary side elevational View of the handgrip portion of a hand manipulatable tool, such as an electric drill, with one shell or casing half of the handgrip yportion of the tool being removed to expose the present invention;

FIG. 2 is a section taken along line 2 2 of FIG. 1;

FIG. 3 is an enlarged section taken along line 3 3 of FIG. 1; and

FIG. 4 is a circuit drawing diagrammatically showing the present inventionvin association with a silicon controlled rectifier speed control circuit.

Referring now to FIGS. 1 and 2, the present invention will be seen to be incorporated in a handle or handgrip portion of a hand manipulatable power tool, such as an electric drill generally designated 10. The handle portion of the drill consists of housing halves or shells 11 and 12 which are opposite hand versions of each other and are identical with the exception of minor details. Housing shell 11 is not shown in FIG. 1 in the interest of better illustration of the invention; this housing shell is illustrated in phantom lines in FIG. 2. It will be understood that the portion of drill which is not illustrated is of conventional construction, i.e., it includes a forwardly extending housing portion enclosing a suitable electric motor and means for drivingly connecting the latter with the drill chuck. Housing shells 11 and 12 each include a recess or cut-out in their edges defining a trigger receiving opening 14. Also, shells 1l and 12 each include a semi-circular cut-out in their edges defining an opening for reception of a fitting 15 at one end of an electric cord 16.

The present invention includes a housing or casing, generally designated 18, having side walls 19 and 20 defining a guideway or channel slidably supporting a trigger 21, which trigger extends through opening 14 of the tool housvtween side walls 19 and 20. In the surface, which cross-cut receives 3,328,6l3 Patented June 27, 1967 ing. Casing 18 may be mounted in the handle portion of the drill by any suitable means (not shown). Preferably, casing 18 and its associated components are removably or detachably mounted in the tool housing. The casing includes a rear wall 22 which is in abutting engagement with one end of a coil spring 24. The other end of spring 24 is received within a blind bore 25 in trigger 21. Spring 24 is arranged to bias or urge the trigger outwardly of the tool handle to the off position, 1'.e., to the right as illustrated in FIG. 1.

Casing wall 20 includes an upwardly directed extension 20a which mounts a rotary potentiometer or variable resistor 27. The potentiometer 27 is mounted with its rotary element 28 disposed over the trigger at right angles with the direction of movement of the latter. Rotary potentiometer 27, which may be of known construction, includes terminals 30, 31 and 32.

A gear 34 is fixed on rotary element 28 of the potentiometer. Trigger 21 includes a series of integral gear teeth 35 in its upper surface, which teeth are in meshing engagement with the teeth of gear 34. Teeth 35 extend in a rectilinear manner in a direction parallel to the direction of movement of trigger 21; accordingly, movement of trigger 21 causes movement or rotation of rotary element 28 of the potentiometer. Spring 24 or casing wall 22 may serve as a stop to limit inward movement of trigger 21. A suitable stop (not shown) may be provided on housing 18 to limit outward movement of trigger 21, or outward movement of the trigger may be limited or stopped by the potentiometer itself, i.e., by the rotary element of the potentiometer reaching its stop.

Housing 18 includes a partition or wall 37 and a bottom wall 38, which walls define a lower compartment beembodiment of the invention illustrated, this compartment houses the components of an associated speed control circuit, viz., a silicon controlled rectifier 39, a capacitor 40, a voltage responsive device 41 of the type adapted to become conductive upon application thereto of a predetermined voltage (e.g. a gas filled neon bulb or an avalanche type diode), and a fixed resistor 42 (FIG. 2).l

Referring now to FIG. 3, wall or partition 37, which is formed of dielectric material, mounts a contact strip 44, a shorter juxtaposed contact strip 45 and a contact button 46 aligned with contact strip 45 and spaced from one end of the latter. Trigger 21 includes a cross-cut 47 in its undera contact roller 48. Contact roller 48 is arranged at right angles with contact vstrips 44, 45 and is arranged to roll along the latter during movement of the trigger. A small spring 49 (FIG. 2) is provided for urging contact roller 48 into engagement with contact strips 44, 45 and contact 46.

Contact roller 48 is arranged so that one end thereof is always in rolling engagement with contact strip 44. Upon initial rearward movement of the trigger, contact roller 48 comes into engagement with contact strip 45. Contact roller 48 remains in engagement with contact strip 45 during continued rearward movement of the trigger. When trigger 21 is pulled or squeezed to its rearwardmost position, contact roller 48 passes from strip 45 and comes into engagement with contact 46. The reason for this relationship between contact roller 48 and the various contacts will be explained hereinbelow in connection with the description of the associated circuit.

FIG. 2 illustrates a trigger locking button 50 which iS mounted within a cylindrical member 51 and which extends through a suitable opening 52 formed in casing shell 12. Locking button 50 is adapted to lock trigger 21 in its full in position wherein contact roller 48 extends across contact strip 44 and contact button 46. Locking button 50 will not be described in detail as it may be of known construction and of itself forms no part of the present invention.

FIG. 4 illustrates a silicon controlled rectifier speed control circuit with which the present invention is asso- Vciated in its preferred form. This circuit itself forms the subject matter of Gawron application, Ser. No. 226,- 956, filed Sept. 28, 1962. Reference characters S4 and 55 designate conductors energized from a suitable source of 60 cycle alternating current operating at a convention voltage in the order of 117 volts. `Conductor 54 is directly connected with contact strip 44. Conductor 55 extends to motor 56-a series type universal motor, for example. A line 57 extends from the motor to contact 46. Capacitor 40 and fixed resistor 42 are arranged in series circuit relation in a line 58 which extends from line 57 to one terminal of potentiometer 27. A line 59 connects another terminal of the potentiometer with the anode of silicon controlled rectier 39. The cathode of the silicon controlled rectifier is connected to line 57 by a line 60. Bulb 41 is connected in a line 61 extending from the gate of the silicon controlled rectifier 39 to a common connection with line 58 between the capacitor 40 and resistor 42. Another line 62 connects line 59 with contact strip 45.

In operation, When the trigger is fully extended, contact roller 48, although in engagement with contact strip 44, is not in engagement with either contact strip 45 or contact I46. In other words, the circuit to the motor is open, i.e., the trigger is in its off position. After the trigger is initially squeezed or moved inwardly, contact roller 48 comes into engagement with the end of contact strip 45 remote from contact 46 thereby energizing the tool motor through the silicon controlled rectifier speed control circuit. By reason of the engagement between gear 34 and teeth 35 of the trigger, movement of the trigger causes actuation or operation of rotary potentiometer 27. Depending on the extent to which the trigger is pressed, the rotary potentiometer 27 is varied or shifted to vary the voltage that is applied to the capacitor 40 for determining the time'in the half cycle (that is adapted to be conducted by the silicon controlled rectifier 39) that current ispermitted to fiow to the armature of tool motor 56. Potentiometer 27 is arranged so that the higher resistance values are obtained when the trigger is extended and the resistance is thereby decreased as the trigger is squeezed. As the trigger 21 is squeezed, the speed of the motor is increased. For a detailed explanation of the operation of the circuit, reference should be had to the aforementioned Gawron patent.

Thus it will be seen that the present invention provides a unique way of connecting the trigger with the rotary potentiometer or variable resistor thereby to provide positive control of the latter upon manipulation of the former. The present invention also provides a compact, trigger operated, speed control switch unit which may be readily mounted in a tool housing, such as the handle portion of a drill.

While the invention has been shown in only but one form, it will be obvious to those skilled in the art that it is not to be so limited. On the contrary, the invention is susceptible of various forms and modifications without departing from the spirit and scope of the appended claims. It will be appreciated that the present invention may be used in association with any speed control circuit having a rotary potentiometer as one component thereof. Accordingly, the invention is not to be limited for use with the speed control circuit shown in FIG. 4.

I claim:

1. A speed control unit for an electrically operated hand manipulatable tool, said unit comprising, a casing adapted to be mounted in the housing of said tool, a trigger movably mounted on said casing for oscillating movement, a rotary potentiometer mounted on said casing in adjacent relation with said trigger, one or more components in said casing defining an electrical circuit connected with said potentiometer, which circuit is adapted to control the speed of an associated tool motor, a gear fixed on the rotary element of said potentiometer, a series of gear teeth on said trigger and extending along the direction of movement thereof, which gear teeth are in engagement With said gear and are thereby adapted to rotate said rotary element of the potentiometer upon actuation of said trigger.

2. The speed control unit according to claim 1 wherein said circuit includes a controllable semi-conductor as one component thereof.

3. A variable speed control unit for a hand tool powered by an electric motor, which tool includes a housing having a handgrip portion provided with an opening to receive an operating trigger, said unit comprising, a casing adapted to be mounted in said handgrip housing portion, a trigger mounted on the casing for oscillating movement through said opening, a plurality of electrical components carried by said casing and defining a speed control circuit, and a rotary potentiometer arranged in said circuit so that operation of the former varies the speed of the associated tool motor, said potentiometer being mounted on said casing in adjacent relationship wtih said trigger, an arcuate gear formation on the rotary element of said potentiometer, a series of gear teeth on said triggerV for movement therewith, which teeth are in meshing engagement with said gear formation thereby adapting the trigger for actuation of said potentiometer.

4. The unit according to claim 3 wherein said circuit includes as one component thereof a controllable semiconductor.

No references cited.

ORIS L. RADER, Primary Examiner.

G. SIMMONS, Assistant Examiner.

Notice of Adverse Decision in Interference In Interference No. 96,319 nvolvn Patent No. 3,328,613, A. F. Gawron, SPEED CONTROL SYSTEM F R ELECTRICALY POWERED TOOLS OF THE TRIGGER CONTROLLED TYPE, final judgment adverse to the patente@l was rendered July 23, 1970, as to claims 1-4.

[Oficial Gazette Jam 8, 1971.] 

1. A SPEED CONTROL UNIT FOR AN ELECTRICALLY OPERATED HAND MANIPULATABLE TOOL, SAID UNIT COMPRISING, A CASING ADAPTED TO BE MOUNTED IN THE HOUSING OF SAID TOOL, A TRIGGER MOVABLY MOUNTED ON SAID CASING FOR OSCILLATING MOVEMENT, A ROTARY POTENTIOMETER MOUNTED ON SAID CASING IN ADJACENT RELATION WITH SAID TRIGGER, ONE OR MORE COMPONENTS IN SAID CASING DEFINING AN ELECTRICAL CIRCUIT CONNECTED WITH SAID POTENTIOMETER, WHICH CIRCUIT IS ADAPTED TO CONTROL THE SPEED OF AN ASSOCIATED TOOL MOTOR, A GEAR FIXED ON THE ROTARY ELEMENT OF SAID POTENTIOMETER, A SERIES OF GEAR TEETH ON SAID TRIGGER AND EXTENDING ALONG THE DIRECTION OF MOVEMENT THEREOF, WHICH GEAR TEETH ARE IN ENGAGEMENT WITH SAID GEAR AND ARE THEREBY ADAPTED TO ROTATE SAID ROTARY ELEMENT OF THE POTENTIOMETER UPON ACTUATION OF SAID TRIGGER. 